Inhibition of autophagic turnover in ß-cells by fatty acids and glucose leads to apoptotic cell death.

Autophagy, a cellular recycling process responsible for turnover of cytoplasmic contents, is critical for maintenance of health. Defects in this process have been linked to diabetes. Diabetes-associated glucotoxicity/lipotoxicity contribute to impaired ß-cell function and have been implicated as contributing factors to this disease. We tested the hypothesis that these two conditions affect ß-cell function by modulating autophagy. We report that exposure of ß-cell lines and human pancreatic islets to high levels of glucose and lipids blocks autophagic flux and leads to apoptotic cell death. EM analysis showed accumulation of autophagy intermediates (autophagosomes), with abundant engulfed cargo in palmitic acid (PA)- or glucose-treated cells, indicating suppressed autophagic turnover. EM studies also showed accumulation of damaged mitochondria, endoplasmic reticulum distention, and vacuolar changes in PA-treated cells. Pulse-chase experiments indicated decreased protein turnover in ß-cells treated with PA/glucose. Expression of mTORC1, an inhibitor of autophagy, was elevated in ß-cells treated with PA/glucose. mTORC1 inhibition, by treatment with rapamycin, reversed changes in autophagic flux, and cell death induced by glucose/PA. Our results indicate that nutrient toxicity-induced cell death occurs via impaired autophagy and is mediated by activation of mTORC1 in ß-cells, contributing to ß-cell failure in the presence of metabolic stress.

WS6 induces both alpha and beta cell proliferation without affecting differentiation or viability.

Agents that stimulate human pancreatic beta cell proliferation are needed to improve diabetes mellitus treatment. Recently, a small molecule, WS6, was observed to stimulate human beta cell proliferation. However, little is known about its other effects on human islets. To better understand the role of WS6 as a possible beta cell regenerative therapy, we carried out in-depth phenotypic analysis of WS6-treated human islets, exploring its effects on non-beta cell proliferation, beta cell differentiation, and islet cell viability. WS6 not only stimulated beta cell proliferation in cultured human islets (in agreement with previous reports), but also human alpha cell proliferation, indicating that WS6 is not a beta cell-specific mitogen. WS6 did not change the proportion of insulin-positive beta cells or the expression of beta cell-specific transcription factors, suggesting that WS6 does not alter beta cell differentiation, and WS6 had no effect on human islet cell apoptosis or viability. In conclusion, WS6 stimulates proliferation of both human beta and alpha cells while maintaining cellular viability and the beta cell differentiated phenotype. These findings expand the literature on WS6 and support the suggestion that WS6 may help increase human islet mass needed for successful treatment of diabetes.

IL-18 is required for self-reactive T cell expansion in NOD mice.

IL-18 has a well-established role in pro-inflammatory responses in the islets in type 1 diabetes. Here, we identify a distinctive role for IL-18 in expanding pathogenic T cells in the periphery of NOD mice. Well in advance of disease onset, the periphery of IL-18-deficient mice exhibits reduced T cell turnover, an increased prevalence of naïve and quiescent T cells, emergence of fewer effector T cells, and disease protection. Islet-reactive T cells fail to become activated in the lymphoid organs of mice lacking IL-18 and their rapid expansion is inhibited. IL-18 secretion by antigen presenting cells increases with advancing disease and is required for expression of its receptor on T cells. Our results demonstrate that induction of the IL-18 receptor reflects a critical stage of autoreactive T cell activation and expansion on the pathway toward effector T cell differentiation. This study therefore assigns a novel role to IL-18 for expanding the pool of islet-destructive T cells during pre-diabetes. This report highlights a new basic mechanism in type 1 diabetes pathogenesis and suggests that targeting the IL-18 pathway should be explored as a potential treatment strategy.

Heightened Levels of Antimicrobial Response Factors in Patients With Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a chronic progressive autoimmune disease leading to considerable disability over time. The disease can be characterized by the presence of multiple autoantibodies in the serum and synovial fluid. Microbial dysbiosis is proposed to play a role in the pathogenesis of RA. Increased systemic bacterial exposure leads to elevated levels of antimicrobial response factors (ARFs) in the circulation. In the present study, we tested whether RA patients have increased levels of ARFs by analyzing the levels of multiple ARFs in serum from RA patients and healthy age and sex-matched controls. The levels of soluble CD14 (sCD14), lysozyme, and CXCL16 were significantly elevated in RA patients compared to healthy controls. Lipopolysaccharide binding protein (LBP) levels remained unchanged in RA patients compared to healthy controls. A positive correlation of LBP with rheumatoid factor (RF) was also found in RA subjects. Interestingly, the levels of anti-endotoxin core antibodies (EndoCAb) IgM, total IgM, EndoCAb IgA, and total IgA were significantly elevated in RA patients compared to healthy controls. No significant changes in the levels of EndoCAb IgG and total IgG were observed in RA patients compared to healthy controls. Furthermore, lysozyme and CXCL16 levels were positively correlated with disease severity among RA subjects. Increases in the levels of several ARFs and their correlations with clinical indices suggest systemic microbial exposure in the RA cohort. Modulation of microbial exposure may play an important role in disease pathogenesis in individuals with RA.

Current understanding of the role of gut dysbiosis in type 1 diabetes.

Type 1 diabetes (T1D) is a chronic autoimmune disorder that results from destruction of the insulin-producing pancreatic ß-cells. The disease mainly affects juveniles. Changes in the composition of the gut microbiota (dysbiosis) and changes in the properties of the gut barrier have been documented in T1D subjects. Because these factors affect immune system functions, they are likely to play a role in disease pathogenesis. However, their exact role is currently not fully understood and is under intensive investigation. In this article we discuss recent advancements depicting the role of intestinal dysbiosis on immunity and autoimmunity in T1D. We also discuss therapies aimed at maintaining a healthy gut barrier as prevention strategies for T1D.

Human Islet Response to Selected Type 1 Diabetes-Associated Bacteria: A Transcriptome-Based Study.

Type 1 diabetes (T1D) is a chronic autoimmune disease that results from destruction of pancreatic ß-cells. T1D subjects were recently shown to harbor distinct intestinal microbiome profiles. Based on these findings, the role of gut bacteria in T1D is being intensively investigated. The mechanism connecting intestinal microbial homeostasis with the development of T1D is unknown. Specific gut bacteria such as Bacteroides dorei (BD) and Ruminococcus gnavus (RG) show markedly increased abundance prior to the development of autoimmunity. One hypothesis is that these bacteria might traverse the damaged gut barrier, and their constituents elicit a response from human islets that causes metabolic abnormalities and inflammation. We have tested this hypothesis by exposing human islets to BD and RG in vitro, after which RNA-Seq analysis was performed. The bacteria altered expression of many islet genes. The commonly upregulated genes by these bacteria were cytokines, chemokines and enzymes, suggesting a significant effect of gut bacteria on islet antimicrobial and biosynthetic pathways. Additionally, each bacteria displayed a unique set of differentially expressed genes (DEGs). Ingenuity pathway analysis of DEGs revealed that top activated pathways and diseases included TREM1 signaling and inflammatory response, illustrating the ability of bacteria to induce islet inflammation. The increased levels of selected factors were confirmed using immunoblotting and ELISA methods. Our data demonstrate that islets produce a complex anti-bacterial response. The response includes both symbiotic and pathogenic aspects. Both oxidative damage and leukocyte recruitment factors were prominent, which could induce beta cell damage and subsequent autoimmunity.

Coordinated Induction of Antimicrobial Response Factors in Systemic Lupus Erythematosus.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by dysregulated autoantibody production and complement activation leading to multi-organ damage. The disease is associated with increased intestinal permeability. In this study, we tested the hypothesis that SLE subjects have increased systemic exposure to bacteria. Since bacteria induce the expression of antimicrobial response factors (ARFs), we measured the levels of a series of clinically relevant ARFs in the plasma of SLE subjects. We found that levels of sCD14, lysozyme, and CXCL16 were significantly elevated in SLE subjects. A strong positive correlation was also observed between sCD14 and SELENA-SLEDAI score. Interestingly, the ratio of EndoCAb IgM:total IgM was significantly decreased in SLE and this ratio was negatively correlated with sCD14 levels. Although, there were no significant differences in the levels of lipopolysaccharide binding protein (LBP) and fatty acid binding protein 2 (FABP2), we observed significant positive correlations between lysozyme levels and sCD14, LBP, and FABP2. Moreover, galectin-3 levels also positively correlate with lysozyme, sCD14, and LBP. Since our SLE cohort comprised 43.33% males, we were able to identify gender-specific changes in the levels of ARFs. Overall, these changes in the levels and relationships between ARFs link microbial exposure and SLE. Approaches to reduce microbial exposure or to improve barrier function may provide therapeutic strategies for SLE patients.

Distinct regulation of autoreactive CD4 T cell expansion by interleukin-4 under conditions of lymphopenia.

IL-4 is protective against Type 1 diabetes in the NOD mouse. IL-4 promotes T cell survival in vitro, but little is known about the effect of IL-4 on clonal expansion in vivo. Here, we show that IL-4 only enhances the expansion of autoreactive CD4 T cells during lymphopenia and that neither the presence of islet IL-4 nor IL-4 deficiency affects T cell expansion significantly under conditions of immunosufficiency. The accumulation of proliferating cells induced by IL-4 in a lymphopenic host is inhibited incrementally by increasing the number of bystander cells and is prevented by cell numbers well below that of unmanipulated NOD mice. The ability of IL-4 to promote autoreactive CD4 T cell expansion is therefore sensitive to the degree of host immunodeficiency. Paradoxically, IL-4 receptor-deficient, autoreactive CD4 T cells proliferate more extensively than wild-type T cells in immunodeficient hosts, suggesting that the growth-promoting effect of islet IL-4 acts indirectly. These results suggest that IL-4-mediated protection against autoimmunity and diabetes may be outweighed during immunodeficiency by a pathogenic, IL-4-induced expansion of autoreactive T cells.

Interleukin (IL)-18 Binding Protein Deficiency Disrupts Natural Killer Cell Maturation and Diminishes Circulating IL-18.

The cytokine interleukin (IL)-18 is a crucial amplifier of natural killer (NK) cell function. IL-18 signaling is regulated by the inhibitory effects of IL-18 binding protein (IL-18BP). Using mice deficient in IL-18BP (IL-18BPKO), we investigated the impact of mismanaged IL-18 signaling on NK cells. We found an overall reduced abundance of splenic NK cells in the absence of IL-18BP. Closer examination of NK cell subsets in spleen and bone marrow using CD27 and CD11b expression revealed that immature NK cells were increased in abundance, while the mature population of NK cells was reduced. Also, NK cells were polarized to greater production of TNF-α, while dedicated IFN-γ producers were reduced. A novel subset of IL-18 receptor α- NK cells contributed to the expansion of immature NK cells in IL-18BPKO mice. Splenocytes cultured with IL-18 resulted in alterations similar to those observed in IL-18BP deficiency. NK cell changes were associated with significantly reduced levels of circulating plasma IL-18. However, IL-18BPKO mice exhibited normal weight gain and responded to LPS challenge with a >10-fold increase in IFN-γ compared to wild type. Finally, we identified that the source of splenic IL-18BP was among dendritic cells/macrophage localized to the T cell-rich regions of the spleen. Our results demonstrate that IL-18BP is required for normal NK cell abundance and function and also contributes to maintaining steady-state levels of circulating IL-18. Thus, IL-18BP appears to have functions suggestive of a carrier protein, not just an inhibitor.

Exploiting Expression of Hippo Effector, Yap, for Expansion of Functional Islet Mass.

Loss of pancreas ß-cell function is the precipitating factor in all forms of diabetes. Cell replacement therapies, such as islet transplantation, remain the best hope for a cure; however, widespread implementation of this method is hampered by availability of donor tissue. Thus, strategies that expand functional ß-cell mass are crucial for widespread usage in diabetes cell replacement therapy. Here, we investigate the regulation of the Hippo-target protein, Yes-associated protein (Yap), during development of the endocrine pancreas and its function after reactivation in human cadaveric islets. Our results demonstrate that Yap expression is extinguished at the mRNA level after neurogenin-3-dependent specification of the pancreas endocrine lineage, correlating with proliferation decreases in these cells. Interestingly, when a constitutively active form of Yap was expressed in human cadaver islets robust increases in proliferation were noted within insulin-producing ß-cells. Importantly, proliferation in these cells occurs without negatively affecting ß-cell differentiation or functional status. Finally, we show that the proproliferative mammalian target of rapamycin pathway is activated after Yap expression, providing at least one explanation for the observed increases in ß-cell proliferation. Together, these results provide a foundation for manipulating Yap activity as a novel approach to expand functional islet mass for diabetes regenerative therapy.

Altered CD161 bright CD8+ mucosal associated invariant T (MAIT)-like cell dynamics and increased differentiation states among juvenile type 1 diabetics.

Type 1A diabetes (T1D) is believed to be caused by immune-mediated destruction of ß-cells, but the immunological basis for T1D remains controversial. Microbial diversity promotes the maturation and activation of certain immune subsets, including CD161 bright CD8+ mucosal associated invariant T (MAIT) cells, and alterations in gut mucosal responses have been reported in type 1 diabetics (T1Ds). We analyzed T cell populations in peripheral blood leukocytes from juvenile T1Ds and healthy controls. We found that proportion and absolute number of MAIT cells were similar between T1Ds and controls. Furthermore, while MAIT cell proportions increased with age among healthy controls, this trend was not observed among long-standing T1Ds. Additionally, the CD27- MAIT cell subset is significantly increased in T1Ds and positively correlated with HbA1c levels. However, after T1Ds are stratified by age, the younger group has significantly increased proportions of CD27- MAIT cells compared to age-matched controls, and this proportional increase appears to be independent of HbA1c levels. Finally, we analyzed function of the CD27- MAIT cells and observed that IL-17A production is increased in CD27- compared to CD27+ MAIT cells. Overall, our data reveal disparate MAIT cell dynamics between T1Ds and controls, as well as signs of increased MAIT cell activation in T1Ds. These changes may be linked to hyperglycemia and increased mucosal challenge among T1Ds.

Increased expression of IL-18 in the serum and islets of type 1 diabetics.

Type 1 diabetes (T1D) is a chronic disease characterized by autoimmune-mediated destruction of pancreatic insulin-producing beta cells. Interleukin (IL)-18 is a pro-inflammatory cytokine implicated in the pathogenesis of a number of inflammatory diseases. Here, we analyzed IL-18 levels in the plasma of juveniles with T1D. Compared to control subjects, IL-18 levels were significantly elevated in patients with T1D. On the other hand, levels of IL-18 binding protein (IL-18BP) and IL-37, two negative regulators of IL-18 function, remained unchanged when comparing T1D to control samples. Notably, however, although IL-18BP levels were not elevated, IL-18 and IL-18BP were found to be positively correlated in type 1 diabetics. Even so, free, unbound IL-18 remained significantly increased in diabetic patients. Additionally, correlation studies also revealed that IL-18 and IL-18BP are positively correlated with HbA1c levels in T1D patients, suggesting a potential link between IL-18 and metabolic control in these patients. Finally, we observed a significant increase in IL-18 protein expression within human pancreatic islet specimens collected from type 1 diabetics. These results further expand our knowledge of the role of IL-18 in T1D, may give insight into common pathogenic mechanisms associated with metabolic control in both T1D and T2D, and suggest that targeting this cytokine may improve therapeutic outcomes for T1D patients.

CD28⁻ CD8⁺ T cells are significantly reduced and correlate with disease duration in juveniles with type 1 diabetes.

Type 1 diabetes (T1D) is a chronic disease caused by autoimmune destruction of insulin-producing pancreatic ß-cells. T1D is typically diagnosed in children, but information regarding immune cell subsets in juveniles with T1D is scarce. Therefore, we studied various lymphocytic populations found in the peripheral blood of juveniles with T1D compared to age-matched controls (ages 2-17). One population of interest is the CD28(-) CD8(+) T cell subset, which are late-differentiated cells also described as suppressors. These cells are altered in a number of disease states and have been shown to be reduced in adults with T1D. We found that the proportion of CD28(-) cells within the CD8(+) T cell population is significantly reduced in juvenile type 1 diabetics. Furthermore, this reduction is not correlated with age in T1D juveniles, although a significant negative correlation between proportion CD28(-) CD8(+) T cells and age was observed in the healthy controls. Finally, correlation analysis revealed a significant and negative correlation between the proportion of CD28(-) CD8(+) T cells and T1D disease duration. These findings show that the CD28(-) CD8(+) T cell population is perturbed following onset of disease and may prove to be a valuable marker for monitoring the progression of T1D.

TLR signaling controls lethal encephalitis in WNV-infected brain.

Toll-like receptors (TLRs) are known to be activated in Central Nervous System (CNS) viral infections and are recognized to be a critical component in innate immunity. Several reports state a role for particular TLRs in various CNS viral infections. However, excessive TLR activation was previously reported by us in correlation with a pathogenic, rather than a protective, outcome, in a model of SIV encephalitis. Here we aimed at understanding the impact of TLR-mediated pathways by evaluating the early course of pathogenesis in the total absence of TLR signaling during CNS viral infections. We utilized a mouse model of sublethal West Nile virus (WNV) infection. WNV is an emerging neurotropic flavivirus, and a significant global cause of viral encephalitis. The virus was peripherally injected into animals that simultaneously lacked two key adapter molecules of TLR signaling, MyD88 and TRIF. On day 2 pi (post infection), MyD88/Trif-/- mice showed an increased susceptibility to WNV infection, and revealed an impairment in innate immune cytokines, when compared to wild type mice (WT). By day 6 pi, there was an increase in viral burden and robust expression of inflammatory cytokines as well as higher cell infiltration into the CNS in MyD88/Trif-/-, when compared to infected WT. A drastic increase in microglia activation, astrogliosis, and inflammatory trafficking were also observed on day 6 pi in MyD88/Trif-/-. Our observations show a protective role for TLR signaling pathways in preventing lethal encephalitis at early stages of WNV infection.

TGF-ß superfamily member Nodal stimulates human ß-cell proliferation while maintaining cellular viability.

In an effort to expand human islets and enhance allogeneic islet transplant for the treatment of type 1 diabetes, identifying signaling pathways that stimulate human ß-cell proliferation is paramount. TGF-ß superfamily members, in particular activin-A, are likely involved in islet development and may contribute to ß-cell proliferation. Nodal, another TGF-ß member, is present in both embryonic and adult rodent islets. Nodal, along with its coreceptor, Cripto, are pro-proliferative factors in certain cell types. Although Nodal stimulates apoptosis of rat insulinoma cells (INS-1), Nodal and Cripto signaling have not been studied in the context of human islets. The current study investigated the effects of Nodal and Cripto on human ß-cell proliferation, differentiation, and viability. In the human pancreas and isolated human islets, we observed Nodal mRNA and protein expression, with protein expression observed in ß and α-cells. Cripto expression was absent from human islets. Furthermore, in cultured human islets, exogenous Nodal stimulated modest ß-cell proliferation and inhibited α-cell proliferation with no effect on cellular viability, apoptosis, or differentiation. Nodal stimulated the phosphorylation of mothers against decapentaplegic (SMAD)-2, with no effect on AKT or MAPK signaling, suggesting phosphorylated SMAD signaling was involved in ß-cell proliferation. Cripto had no effect on human islet cell proliferation, differentiation, or viability. In conclusion, Nodal stimulates human ß-cell proliferation while maintaining cellular viability. Nodal signaling warrants further exploration to better understand and enhance human ß-cell proliferative capacity.

Altered RECQ Helicase Expression in Sporadic Primary Colorectal Cancers.

Deregulation of DNA repair enzymes occurs in cancers and may create a susceptibility to chemotherapy. Expression levels of DNA repair enzymes have been shown to predict the responsiveness of cancers to certain chemotherapeutic agents. The RECQ helicases repair damaged DNA including damage caused by topoisomerase I inhibitors, such as irinotecan. Altered expression levels of these enzymes in colorectal cancer (CRC) may influence the response of the cancers to irinotecan. Thus, we assessed RECQ helicase (WRN, BLM, RECQL, RECQL4, and RECQL5) expression in primary CRCs, matched normal colon, and CRC cell lines. We found that BLM and RECQL4 mRNA levels are significantly increased in CRC (P = .0011 and P < .0001, respectively), whereas RECQL and RECQL5 are significantly decreased (P = .0103 and P = .0029, respectively). RECQ helicase expression patterns varied between specific molecular subtypes of CRCs. The mRNA and protein expression of the majority of the RECQ helicases was closely correlated, suggesting that altered mRNA expression is the predominant mechanism for deregulated RECQ helicase expression. Immunohistochemistry localized the RECQ helicases to the nucleus. RECQ helicase expression is altered in CRC, suggesting that RECQ helicase expression has potential to identify CRCs that are susceptible to specific chemotherapeutic agents.

Hippo signaling regulates pancreas development through inactivation of Yap.

The mammalian pancreas is required for normal metabolism, with defects in this vital organ commonly observed in cancer and diabetes. Development must therefore be tightly controlled in order to produce a pancreas of correct size, cell type composition, and physiologic function. Through negative regulation of Yap-dependent proliferation, the Hippo kinase cascade is a critical regulator of organ growth. To investigate the role of Hippo signaling in pancreas biology, we deleted Hippo pathway components in the developing mouse pancreas. Unexpectedly, the pancreas from Hippo-deficient offspring was reduced in size, with defects evident throughout the organ. Increases in the dephosphorylated nuclear form of Yap are apparent throughout the exocrine compartment and correlate with increases in levels of cell proliferation. However, the mutant exocrine tissue displays extensive disorganization leading to pancreatitis-like autodigestion. Interestingly, our results suggest that Hippo signaling does not directly regulate the pancreas endocrine compartment as Yap expression is lost following endocrine specification through a Hippo-independent mechanism. Altogether, our results demonstrate that Hippo signaling plays a crucial role in pancreas development and provide novel routes to a better understanding of pathological conditions that affect this organ.

Type 1 diabetes: role of intestinal microbiome in humans and mice.

Type 1 diabetes is a disease involving autoimmune destruction of pancreatic beta cells in genetically predisposed individuals. Identifying factors that trigger initiation and progression of autoimmunity may provide opportunities for directed prophylactic and therapeutic measures to prevent and/or treat type 1 diabetes. The human intestinal microbiome is a complex, symbiotic ecological community that influences human health and development, including the development and maintenance of the human immune system. The role of the intestinal microbiome in autoimmunity has garnered significant attention, and evidence suggests a particular role for intestinal microbiome alterations in autoimmune disease development, including type 1 diabetes. This review will examine the role of the intestinal microbiome in the development and function of the immune system and how this relates to the development of autoimmunity. Data from animal and human studies linking alterations in the intestinal microbiome and intestinal integrity with type 1 diabetes will be closely examined. Finally, we will examine the interactions between the intestinal microbiome and dietary exposures and how these interactions may further influence autoimmunity and type 1 diabetes development.

Differential IL-21 signaling in APCs leads to disparate Th17 differentiation in diabetes-susceptible NOD and diabetes-resistant NOD.Idd3 mice.

Type 1 diabetes (T1D) is an autoimmune disease that shows familial aggregation in humans and likely has genetic determinants. Disease linkage studies have revealed many susceptibility loci for T1D in mice and humans. The mouse T1D susceptibility locus insulin-dependent diabetes susceptibility 3 (Idd3), which has a homologous genetic interval in humans, encodes cytokine genes Il2 and Il21 and regulates diabetes and other autoimmune diseases; however, the cellular and molecular mechanisms of this regulation are still being elucidated. Here we show that T cells from NOD mice produce more Il21 and less Il2 and exhibit enhanced Th17 cell generation compared with T cells from NOD.Idd3 congenic mice, which carry the protective Idd3 allele from a diabetes-resistant mouse strain. Further, APCs from NOD and NOD.Idd3 mice played a central role in this differential Th17 cell development, and IL-21 signaling in APCs was pivotal to this process. Specifically, NOD-derived APCs showed increased production of pro-Th17 mediators and dysregulation of the retinoic acid (RA) signaling pathway compared with APCs from NOD.Idd3 and NOD.Il21r-deficient mice. These data suggest that the protective effect of the Idd3 locus is due, in part, to differential RA signaling in APCs and that IL-21 likely plays a role in this process. Thus, we believe APCs provide a new candidate for therapeutic intervention in autoimmune diseases.

Epithelial progenitor 1, a novel factor associated with epithelial cell growth and differentiation.

The growth and renewal of epithelial tissue is a highly orchestrated and tightly regulated process occurring in different tissue types under a variety of circumstances. We have been studying the process of pancreatic regeneration in mice. We have identified a cell surface protein, named EP1, which is expressed on the duct epithelium during pancreatic regeneration. Whereas it is not detected in the pancreas of normal mice, it is found in the intestinal epithelium of normal adult mice, as well as during pancreatic repair following cerulein-induced destruction of the acinar tissue. The distinctive situations in which EP1 is expressed, all of which share in common epithelial cell growth in the gastrointestinal tract, suggest that EP1 is involved in the growth and renewal of epithelial tissues in both the intestine and the pancreas.